dsa: implement VERIFY-SIGNATURE for DSA public keys

Author: dnaeon

src/cert-key.lisp

@@ -203,7 +203,9 @@ Please refer to [1] for more details.
     (:name "rsa-sha2-256"
      :digest :sha256)
     (:name "rsa-sha2-512"
-     :digest :sha512))
+     :digest :sha512)
+    (:name "ssh-dss"
+     :digest :sha1))
   "OpenSSH certificate signature types")
 
 (defun get-signature-type (value)

src/dsa.lisp

@@ -29,6 +29,9 @@
   ()
   (:documentation "Represents an OpenSSH DSA public key"))
 
+(defmethod verify-signature ((key dsa-public-key) message signature digest-spec)
+  (ironclad:verify-signature key (ironclad:digest-sequence digest-spec message) signature))
+
 (defmethod rfc4251:decode ((type (eql :dsa-public-key)) stream &key kind comment)
   "Decodes a DSA public key from the given binary stream as defined in FIPS-186-2"
   (unless kind

src/rsa.lisp

@@ -67,6 +67,7 @@
   (:documentation "Represents an OpenSSH RSA private key"))
 
 (defmethod verify-signature ((key rsa-public-key) message signature digest-spec)
+  "Verifies the message using the signature and digest-spec as described in RFC 4253, section 6.6"
   (rsassa-pkcs1-v1_5-verify key message signature digest-spec))
 
 (defmethod rfc4251:decode ((type (eql :rsa-private-key)) stream &key kind public-key